Bridged metallocene complexes, process for preparing the same and use thereof

ABSTRACT

Provided is a bridged cyclopentadienyl-dicarbollide complex having the formula of {L[(Cp)(C 2 B 9 R 1   10 )]}MR in which Cp is an unsubstituted, alkyl-substituted, aryl-substituted or fused ring cyclopentadienyl, R 1  is hydrogen, or alkyl, L is a bridging unit that bonds to both Cp ring and cage carbon atoms, R is alkyl, aryl or a derivative thereof and M is Ti, Zr or Hf. A process for preparing the complex disclosed herein is also provided.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application No. 60/556,417 filed Mar. 25, 2004, which is explicitly incorporated herein by reference in its entirety.

FIELD OF THE INVENTION

The present invention relates to metallocene complexes which are very active for olefin polymerization. Particularly, the invention relates to bridged metallocene complexes used as a single component of Ziegler-Natta catalysts in chemical industry for replacing conventional metallocene/MAO systems without alteration of existing plants.

BACKGROUND OF THE INVENTION

Existing Group IVB metallocene catalysts for olefin polymerization generally consist of two components, precatalysts and cocatalysts. The precatalyst includes a Group IVB metallocene dichloride or a dialkyl complex composed of two aromatic five-membered ring systems that may be tethered by a bridging unit (ansa metallocene complexes). Aromatic ligands to Group IVB metal can be of the same or different type, including but not limited to: cyclopentadienyl, indenyl, fluorenyl, or their derivatives. The cocatalysts includes normally alumoxane (MAO), modified alumoxane (MMAO) or perfluoro (tetraphenyl)borate. The precatalyst does not show any activity toward olefin polymerization. The cocatalyst is essential to activate the precatalyst.

Al(MAO)/M(Group IVB metal) molar ratio of 1,000 in a Group IVB metallocene catalyst is typical but it can reach 20,000 in some cases (Kaminsky, W.; Arndt, M. Adv. Polym. Sci. 1997, 127, 144; Gladysz, J. A. Guest Editor, Special Issue for Frontiers in Metal-Catalyzed Polymerization. Chem. Rev. 2000, 100 (4)). The disadvantage of the current catalyst system is the incorporation of aluminum or fluorine into the polymer, which can cause serious problems when polyolefins are thermally decomposed.

To overcome these problems, a neutral Group IVB metallocene type of catalysts containing dicarbollide, [(C₅Me₅)(C₂B₉H₁₁)]MMe (M=Ti, Zr, Hf), was developed. Fourteen electron, d⁰ bent-metallocene alkyl complexes of general type (C₅R₅)₂M(R′)⁺ exhibit a rich insertion, olefin polymerization, and C—H activation chemistry which is highly sensitive to the structural and electronic properties of the (C₅R₅)₂M fragment, the presence or absence of Lewis base, and counterion/cocatalyst properties. Replacement of a uni-negative C₅R₅ ⁻ ligand of (C₅R₅)₂M(R′)⁺ by the isolobal, di-negative dicarbollide ligand (C₂B₉H₁₁ ²⁻) reduces the overall charge by one unit but leaves the gross structural and metal frontier orbital properties unchanged.

The resulting neutral mixed sandwich complexes [(C₅Me₅)(C₂B₉H₁₁)]M(R) show a variety of ligand exchange, insertion (alkenes, alkynes etc) and ligand C—H activation reactions characteristics of electrophilic metal alkyls (Crowther, D. J.; Baenziger, N. C.; Jordan. R. F. J. Am. Chem. Soc. 1991, 113, 1455). It is noteworthy that this type of complexes can catalyze the polymerization of ethylene with a moderate activity in the absence of any cocatalysts. The activity was 7.2×10⁴ g of PE/(mol of Zr atom h)(Crowther, D. J.; Baenziger, N. C.; Jordan. R. F. J. Am. Chem. Soc. 1991, 113, 1455). The activity would be increased in the presence of R₃Al (R=alykl).

[(C₅Me₅)(C₂B₉H₁₁)]MMe are not thermally stable and can be converted into {[(C₅Me₅)(C₂B₉H₁₁)]M}₂CH₂ upon heating. The latter is also an active catalyst for ethylene polymerization with a similar activity to its parent complex (Crowther, D. J.; Baenziger, N. C.; Jordan. R. F. J. Am. Chem. Soc. 1991, 113, 1455; Karol, F. J.; Kao, S.-C.; Brady III, R. C. U.S. Pat. No. 5,162,466), which is a significant progress in the field of Ziegler-Natta catalysis (Kaminsky, W.; Arndt, M. Adv. Polym. Sci 1997, 127, 144). This process is of great scientific and technological interests since it can avoid using expense MAO, thus eliminating possible contaminate of alumina in the polymeric materials. However, these catalysts cannot be used in industries due to low activities.

SUMMARY OF THE INVENTION

We have recently developed a linked cyclopentadienyl-dicarbollide ligand system in which the ansa-ligand renders a Group IVB metal complex in a more open coordination sphere, which in turn not only increases significantly catalytic activities in olefin polymerization in comparison with non-bridged systems, but also improves greatly thermal stability of the catalyst itself.

One aspect of the present invention is to provide a novel Group IVB bridged metallocene complex having the formula (I): {L[(Cp)(C₂B₉R¹ ₁₀)]}MR  (I)

-   -   wherein     -   Cp is selected from the group consisting of cyclopentadienyl,         indenyl, tetrahydroindenyl, and fluorenyl, unsubstituted or         substituted by one or more radicals selected from the group         consisting of C₁–C₁₀ alkyl, C₂–C₁₀ alkenyl, C₃–C₁₀ cycloalkyl,         C₁–C₁₀ alkoxy, and C₆–C₁₅ aryl, where each pair of adjacent         radicals on the ring together may form a cyclic group;     -   each R¹ is independently hydrogen, halogen, C₁–C₁₀ alkyl or         C₂–C₁₀ alkenyl;     -   L is C₁–C₄ alkylene unsubstituted or substituted by one or more         radicals selected form the group consisting of C₁–C₁₀ alkyl,         C₂–C₁₀ alkenyl, C₃–C₁₀ cycloalkyl, C₁–C₁₀ alkoxy and C₆–C₁₅         aryl, or Si(R²)₂ where each R² is independently selected from         the group consisting of hydrogen, C₁–C₁₀ alkyl, C₂–C₁₀ alkenyl,         C₁–C₁₀ alkoxy, C₃–C₁₀ cycloalkyl, and C₆–C₁₅ aryl, that bonds to         both the Cp ring and the cage of C₂B₉R¹ ₁₀;     -   R is selected from the group consisting of hydrogen, halogen,         R³, OR³, SR³, NR³R⁴, PR³R⁴, and ZSiR³(R⁴)₂ where each R³ is         independently selected from the group consisting of C₁–C₁₀         alkyl, C₂–C₁₀ alkenyl, C₃–C₁₀ cycloalkyl and C₆–C₁₅ aryl, and         each R⁴ is independently selected from the group consisting of         hydrogen, C₁–C₁₀ alkyl, C₂–C₁₀ alkenyl, C₃–C₁₀ cycloalkyl and         C₆–C₁₅ aryl, and Z is C₁–C₁₀ alkylene; and     -   M is Ti, Zr or Hf.

According to another aspect of the present invention, there is provided a method for the preparation of a bridged metallocene complex of the formula (I), which comprises:

-   -   reacting a protonated form of {L[(Cp)(C₂B₉R¹ ₁₀)]}³⁻ with MR₄         where R is defined above but not halogen, alternatively     -   reacting {L[(Cp)(C₂B₉R¹ ₁₀)]}³⁻ with MX₄ and, if desired,         followed by the substitution of X with R where R is defined         above but not halogen,     -   wherein X is halogen, and Cp, L, R¹ and M are as defined above.

A further aspect of the present invention relates to a process for olefin polymerization comprising contacting one or more olefin monomers with a complex of formula (I).

In some preferred embodiments of the invention, the substituents on the Cp are selected from the group consisting of C₁–C₄ alkyl, C₂–C₄ alkenyl, C₃–C₆ cycloalkyl, C₁–C₄ alkoxy, C₆–C₁₀ aryl. Moreover, each pair of adjacent radicals on the ring together may also form a cyclic group.

In more preferred embodiments, Cp is unsubstituted cyclopentadienyl or indenyl or substitiuted by from one to four substitutes selected from the group consisting of C₁ to C₄ alkyl, C₂ to C₄ alkenyl, C₃ to C₆ cycloalkyl, C₁ to C₄ alkoxy and C₆–C₁₀ aryl. Particular substituents on the Cp are selected from the group consisting of methyl, isopropyl and tert-butyl.

In the invention, R¹ is preferably hydrogen.

In preferred embodiments of the invention, L is C₁–C₄ alkylene unsubstituted or substituted by one or more radicals selected from the group consisting of C₁–C₄ alkyl, C₂–C₄ alkenyl, C₃–C₆ cycloalkyl, C₁–C₄ alkoxy, and C₆–C₁₀ aryl, or Si(R²)₂ where each R² is independently selected from the group consisting of hydrogen, C₁–C₄ alkyl, C₂–C₄ alkenyl, C₃–C₆ cycloalkyl, C₁–C₄ alkoxy, and C₆–C₁₀ aryl. More preferably, L is unsubstituted C₁–C₂ alkylene or substituted by two substitutes selected from C₁–C₄ alkyl. In a specifically preferred embodiment, L is C(CH₃)₂.

R is preferably selected from the group consisting of R³, OR³, SR³, NR³R⁴, PR³R⁴ and ZSiR³(R⁴)₂ where each R³ is independently selected from the group consisting of C₁–C₄ alkyl, C₂–C₄ alkenyl, C₃–C₆ cycloalkyl, and C₆–C₈ aryl, and each R⁴ is independently selected from the group consisting of hydrogen, C₁–C₄ alkyl, C₂–C₄ alkenyl, C₃–C₆ cycloalkyl, and C₆–C₈ aryl, and Z is C₁–C₄ alkylene. More preferably, R is selected from the group consisting of R³, OR³, NR³R⁴ and ZSiR³(R⁴)₂ where each R³ is independently selected from the group consisting of C₁–C₄ alkyl and C₆–C₈ aryl, and each R⁴ is independently selected from the group consisting of hydrogen, C₁–C₄ alkyl and C₆–C₈ aryl, and Z is C₁–C₄ alkylene.

In the invention, M is preferably Zr or Hf.

In further some specific embodiments, M is Zr or Hf, Cp is C₅H₄, C₅Me₄, C₅H₂(Pr^(i))₂, C₅H₂(Bu^(t))₂ or C₉H₆, L is CMe₂, R¹ is hydrogen and R is CH₂Ph, CH₂TMS or NHC₆H₃Me₂-2,6.

In the process of the invention, the olefin monomer is preferably an alpha-olefin.

Complexes of formula (I) according to the invention can be used as a sole active component of a catalyst for olefin polymerization with high activity. In a specific embodiment of the invention, the activity of a complex of formula (I) is 4.64×10⁶ g of PE/(mol of Zr atom-h) in the absence of any cocatalysts. The complexs of the invention as catalysts for olefin polymerization are of good thermal stability, and can be employed in chemical industry without alteration of existing plants.

BRIEF DESCRIPTION OF THE DRAWINGS

For the purpose of illustration, there are depicted in the drawings certain preferred embodiments of the invention. However, the invention is not limited to precise methods and complexes of the embodiments depicted in the drawings. In the drawings:

FIG. 1 illustrates a preferred reaction scheme for producing a bridged cyclopentadienyl dicarbollide metallocene complex of formula (I) using a bridged cyclopentadienyl dicarbollide complex as a starting material;

FIG. 2 illustrates a preferred reaction scheme for producing complexes of formula (I) using a bridged cyclopentadienyl dicarbollide complex as a starting material;

FIG. 3 illustrates another preferred reaction scheme for producing complexes of formula (I) using a disubstituted fulvene as a starting material; and

FIG. 4 illustrates another preferred reaction scheme for producing complexes of formula (I) using a tetrasubstituted fulvene as a starting material.

DETAILED DESCRIPTION OF THE INVENTION

According to an aspect of the present invention, there are provided bridged cyclopentadienyl-dicarbollide metallocene complexs of formula (I): {L[(Cp)(C₂B₉R¹ ₁₀)]}MR  (I) wherein:

-   -   Cp is selected from the group consisting of cyclopentadienyl,         indenyl, tetrahydroindenyl, and fluorenyl, unsubstituted or         substituted by one or more radicals selected from the group         consisting of C₁–C₁₀ alkyl, C₂–C₁₀ alkenyl, C₃–C₁₀ cycloalkyl,         C₁–C₁₀ alkoxy, and C₆–C₁₅ aryl, where each pair of adjacent         radicals on the ring together may form a cyclic group;     -   each R¹ is independently hydrogen, halogen, C₁–C₁₀ alkyl or         C₂–C₁₀ alkenyl;     -   L is C₁–C₄ alkylene unsubstituted or substituted by one or more         radicals selected form the group consisting of C₁–C₁₀ alkyl,         C₂–C₁₀ alkenyl, C₃–C₁₀ cycloalkyl, C₁–C₁₀ alkoxy and C₆–C₁₅         aryl, or Si(R²)₂ where each R² is independently selected from         the group consisting of hydrogen, C₁–C₁₀ alkyl, C₂–C₁₀ alkenyl,         C₁–C₁₀ alkoxy, C₃–C₁₀ cycloalkyl, and C₆–C₁₅ aryl, that bonds to         both Cp ring and the cage of C₂B₉R¹ ₁₀;     -   R is selected from the group consisting of hydrogen, halogen,         R³, OR³, SR³, NR³R⁴, PR³R⁴, and ZSiR³(R⁴)₂ where each R³ is         independently selected from the group consisting of C₁–C₁₀         alkyl, C₂–C₁₀ alkenyl, C₃–C₁₀ cycloalkyl and C₆–C₁₅ aryl, and         each R⁴ is independently selected from the group consisting of         hydrogen, C₁–C₁₀ alkyl, C₂–C₁₀ alkenyl, C₃–C₁₀ cycloalkyl and         C₆–C₁₅ aryl, and Z is C₁–C₁₀ alkylene; and     -   M is Ti, Zr or Hf.

In the invention, the term “alkyl” means straight or branched saturated acyclic radical.

The term “alkenyl” means straight or branched unsaturated acyclic radical with one or more double-bonds.

The term “cycloalkyl” refers to saturated cyclic alkyl.

The term “aryl” means unsaturated radical containing at least three double-bonds and constituting a conjugated system.

-   -   “C₂B_(m)R¹ _(n)” referred to herein means a dicarbollide or a         radical or a negative ion thereof (m=9 or 10, n=10, 11, 12, 13).

Other technical terms or phrases used herein, unless otherwise specified, should be deemed to have the same meaning as those in the art.

As used herein, the following abbreviations have the following meanings. Any abbreviations not defined have their generally accepted meaning.

Me means methyl; Pr^(i) means isopropyl; Bu^(t) means tert-butyl; Ph means phenyl; and TMS means SiMe₃.

A particularly interesting class of metallocenes according to the invention is that of the complexes of formula (I) in which the Cp is C₅H₄, C₅Me₄, C₅H₂(Bu^(t))₂, indenyl or fluorenyl, L is CMe₂, CH₂ or Si(CH₃)₂, and M is Zr or Hf.

Referring to FIGS. 1–4, the present invention is to provide a method for the preparation of bridged metallocene complexes of the formula (I), which comprises:

-   -   reacting a protonated form of {L[(Cp)(C₂B₉R¹ ₁₀)]}³⁻ with MR₄         wherein Cp, L, R¹ and M are as above defined, and R is the same         as defined above, but not halogen, alternatively     -   reacting {L[(Cp)(C₂B₉R¹ ₁₀)]}³⁻ with MX₄ and, if desired,         followed by the substitution of X with R wherein X is halogen         and R is the same as defined above but not halogen, and Cp, L,         R¹ and M are as above defined.

The reaction of substitution of substituents X with substituents R that are defined above but not halogen can be carried out by methods well-known to those skilled in the art. For example, when the desired R substituents are alkyl groups, the metallocenes can be made to react with alkylmagnesium halides (Grignard reagents) or with alkali metal alkyl compounds.

Suitable solvent for the method of the invention is a hydrocarbon solvent such as, for example hexane, cyclohexane, heptane, pentane, toluene or a cyclic or acyclic ether such as diethyl ether, tetrahydrofuran, glymes (e.g. dimethoxyethane), di-n-butyl ether, dioxane, di-isopropyl ether and the like, or a mixture thereof. Preferably, toluene, pentane, tetrahydrofuran or a mixture thereof is used.

In general, an amount of the solvent used ranging from 1 to about 20 times, preferably from 10 to 15 times, the weight of reactants can be effectively employed. However, those skilled in the art will know well that a greater amount of the solvent can also be employed.

The method for preparing a complex of the formula (I) is readily performed at a temperature ranging from as low as about −100° C. to as high as about room temperature. It is preferred to take the reaction at a temperature below room temperature. The reactants are mixed more preferably below −50° C., most preferably below −78° C., and then warmed to room temperature.

As shown in FIG. 1, in a preferred embodiment, said {L[(Cp)(C₂B₉R¹ ₁₀)]}³⁻ is an alkali metal salt of a bridged cyclopentadienyl-dicarbollide ligand of formula (II): L[(Cp)(C₂B₁₀R¹ ₁₁)]  (II) wherein L, Cp and R¹ are as defined above.

The ligand of the formula (II) can be prepared following the methods in Xie, Z. Acc. Chem. Res. 2003, 36, 1, which is incorporated herein by reference, for example by reacting an unsubstituted or substituted fulvene with a lithium dicarbollide at the presence of an acid.

The alkali metal salt of a ligand of the formula (II) can be prepared by reacting alkali metal alkyls or alkali metal hydrides with a complex of formula (III): [L(Cp)(C₂B₉R¹ ₁₁)][R₃ ⁵NH]  (III) wherein R⁵ is alkyl, preferably C₁–C₆ alkyl, and Cp, L and R¹ are as above defined.

The complex of the formula (III) can be prepared by reacting a ligand of formula (II) with R₃ ⁵NHX, wherein X is halogen, and R⁵ is as above defined.

In a further preferred embodiment, the alkali metal salt is a sodium salt and the process for preparing a bridged metallocene complex is performed with MCl₄ and RY in the solution of THF, wherein M is Ti, Zr or Hf, Y is an alkali metal and the group R is CH₂Ph, CH₂SiMe₃ (CH₂TMS) or NHC₆H₃Me₂-2,6.

In another preferred embodiment, the protonated form of {L[(Cp)(C₂B₉R¹ ₁₀)]}³⁻ (as shown in FIG. 1) can be obtained by treating the alkali metal salt of a ligand of the formula (II) with an acid such as H₃PO₄.

The present invention also relates to a process for olefin polymerization comprising contacting one or more olefin monomers with a complex of the formula (I). In the process for the polymerization of olefins according to the invention, the olefin monomer may the same or different. Preferred olefinic monomers are ethylene, alpha olefins such as propylene and 1-butene, cycloolefins and conjugated diolefins, having two to eight carbon atoms. More preferably, the olefin used is ethylene and an alpha olefin including propylene, butane-1, petene-1, and hexene-1.

The complex of the formula (I) can be used in the polymerization directly or by depositing the complex of the formula (I) on inert supports, such as silica, alumina, styrene-divinylvenzene copolymers or polyehtylene.

The amount of the complex of the formula (I) used in the polymerization is well known for those skilled in the art. Generally, a catalytic amount of a complex of the formula (I) will be enough for the polymerization.

Polyethylene has been used in food packaging, coatings, countless molded toys, and other household items, and it is finding its way into the market to replace common materials such as glass, metal, paper, and concrete. The demand for polyethylene has reached 50 million metric tons annually. This invention relates to novel Group IVB metallocene catalysts showing a very high activity in ethylene polymerization under standard testing conditions in the absence of a cocatalyst and there is a possibility for these catalysts to be used in chemical industry without alteration of existing plant. Therefore, this invention will certainly interest polyethylene producers and catalysts makers.

The following examples are designed to illustrate the present invention and are not intended as a limitation upon the scope thereof.

EXAMPLE 1 Preparation of [Me₂C(C₅H₅)(C₂B₉H₁₁)][Me₃NH]

As shown in FIG. 2, to an ethanol (40 mL) solution of Me₂C(C₅H₅)(C₂B₁₀H₁₁) (0.75 g, 3.0 mmol) was added piperidine (7.5 mL, 75.0 mmol). The mixture was refluxed for 2 days. After removal of ethanol and excess piperidine under vacuum, the residue was dissolved in ethanol (5 mL). A saturated trimethylammonium hydride chloride solution was added to give a sticky solid. Recrystallization from acetone/ether afforded colorless crystals (0.72 g, 80%).

¹H NMR (acetone-d₅): δ 6.72 (m), 6.31 (m), 6.24 (m), 6.18 (m), 6.06 (m), 5.88 (m)(3H, C₅H₅, indicating a mixture of allylic and vinylic isomers), 2.99 (s, 9H)((CH₃)₃NH), 2.82 (m, 2H)(C₅H₅), 1.68 (s, 1H)(CH of C₂B₉H₁₁), 1.24 (s, 3H), 1.08 (br s, 1H)(B—H—B).

¹³C NMR (acetone-d₅): δ 161.3, 158.1, 136.0, 132.5, 132.0, 131.0, 124.7, 124.0 (C₅H₅), 45.4 ((CH₃)₃NH), 42.9 (C₅H₅), 41.0, 31.3 ((CH₃)₂C).

¹¹B NMR (acetone-d₅): δ −11.1 (2), −16.1 (2), −18.1 (1), −19.4 (1), −22.8 (1), −33.4 (1), −36.8 (1).

IR (KBr, cm⁻¹): ν 3128 (m), 2965 (m), 2514 (vs), 2313 (w), 1615 (m), 1465 (s), 1377 (m), 1262 (w), 1180 (w), 1027 (m), 982 (m), 797 (m).

Calculated for C₁₃H₃₂B₉N: C, 52.10; H, 10.76; N, 4.67; and found: C, 51.78; H, 10.69; N, 4.88.

EXAMPLE 2 Preparation of [{[(μ-η⁵): η⁵-Me₂C(C₅H₄)(C₂B₉H₁₀)]Na(THF)}{Na(THF)₃}{Na(THF)₂}]₂

To a THF (30 mL) solution of [Me₂C(C₅H₅)(C₂B₉H₁₁)][Me₃NH] (0.47 g, 1.58 mmol) was added NaH (0.32 g, 13.3 mmol) and the reaction mixture was refluxed for 2 days. The excess of NaH was filtered off. The resulting clear brown solution was concentrated to about 10 mL. The title complex was isolated as colorless crystals after this solution stood at room temperature for several days (0.62 g, 51%).

¹H NMR (pyridine-d₅): δ 6.58 (m, 2H), 6.37 (m, 2H)(C₅H₄), 3.66 (m, 28H) (THF), 2.10 (s, 1H)(CH of C₂B₉H_(10),) 1.90 (s, 3H)((CH₃)₂C), 1.63 (m, 31H) (THF+(CH₃)₂C).

¹³C NMR (pyridine-d₅): δ 101.2, 100.9, 100.8 (C₅H₄), 67.2, 25.2 (THF), 61.4 (C₂B₉H₁₀), 31.1, 30.2, 29.9 ((CH₃)₂C).

¹¹B NMR (pyridine-d₅): δ −21.0 (6), −24.6 (2), −44.9 (1).

IR (KBr, cm⁻¹): ν 2962 (s), 2914 (m), 2879 (m), 2503 (vs), 2350 (w), 1637 (w), 1547 (w), 1454 (m), 1382 (w), 1260 (m), 1092 (s), 1039 (vs), 910 (w), 804 (s), 724 (m).

Calculated for C₆₀H₁₂₀B₁₈Na₆O₁₀: C, 54.01; H, 9.07, and found: C, 54.21; H, 9.01.

EXAMPLE 3 Preparation of Me₂C(C₅H₅)(C₂B₉H₁₂)

85% H₃PO₄ (10.20 g, 88.5 mmol) was added to a suspension of [{[(μ-η⁵): η⁵-Me₂C(C₅H₄)(C₂B₉H₁₀)]Na(THF)}{Na(THF)₃}{Na(THF)₂}]₂(1.33 g, 1.0 mmol) in toluene (30 mL). The resulting two-phase mixture was vigorously stirred at room temperature for 2 h. The toluene layer was decanted and the H₃PO₄ layer was extracted with toluene (2×15 mL). The toluene solutions were combined and dried over MgSO₄. After removal of toluene under vacuum, the pale yellow solid was recrystallized from toluene/n-hexane to give the title complex as a yellow solid (0.35 g, 72%).

¹H NMR (CD₂Cl₂): δ 6.57–5.91 (m, 3H), 2.82–2.92 (m, 2H)(C₅H₅), 125 (s, 3H), 1.10 (s, 3H)((CH₃)₂C).

¹¹B NMR (CD₂Cl₂): δ 3.67 (2), −9.58 (2), −13.91 (1), −19.43 (1), −28.56 (3).

IR (KBr, cm⁻¹): ν_(BH) 2550 (s).

Calculated for C₁₀H₂₂B₉: C, 50.13; H, 9.26, and found: C, 50.25; H, 8.96

EXAMPLE 4 Preparation of [η⁵:η⁵-Me₂C(C₅H₄)(C₂B₉H₁₀)]ZrCH₂Ph

To a THF (30 mL) solution of [{[(μ-η⁵):η⁵-Me₂C(C₅H₄)(C₂B₉H₁₀)]Na(THF)}{Na(THF)₃}{Na(THF)₂}]₂ (1.62 g, 1.0 mmmol) was slowly added a suspension of ZrCl₄(THF)₂ (0.76 g, 2.0 mmol) in THF (10 mL) at −78° C. and the mixture was slowly warmed to room temperature and stirred overnight. A THF (10 mL) solution of KCH₂C₆H₅ (0.25 g, 2.0 mmol) was then added dropwise at −78° C. The reaction mixture was slowly warmed to room temperature and stirred for four hours. After removal of the precipitates and 40 mL of THF, the title complex was isolated as orange crystals via hexane vapor diffusion (0.63 g, 75%).

¹H NMR (benzene-d₆): δ 7.48 (m, 2H), 7.31 (m, 2H), 6.92 (m, 1H)(CH₂C₆H₅), 6.68 (m, 1H), 6.27 (m, 1H), 6.24 (m, 1H), 4.93 (m, 1H)(C₅H₄), 2.60 (s, 2H)(CH₂C₆H₅), 1.99 (s, 1H)(CH of C₂B₉H₁₀), 1.41 (s, 3H), 0.84 (s, 3H)((CH₃)₂C).

¹³C NMR (benzene-d₆): δ 155.0, 129.7, 127.1, 126.5, 122.8 (CH₂C₆H₅), 122.5, 121.6, 120.2, 108.6, 107.2 (C₅H₄), 68.3 (CH₂C₆H₅), 66.3, 51.6 (C₂B₉H₁₀), 38.2, 29.3, 26.3 ((CH₃)₂C).

¹¹B NMR (benzene-d₆): δ3.6 (1), −0.2 (1), −2.7 (1), −5.7 (2), −7.7 (1), −11.3 (1), −12.5 (1), −18.3 (1).

IR (KBr, cm⁻¹): ν 2953 (m), 2913 (m), 2533 (s), 1592 (w), 1457 (m), 1259 (s), 1193 (w), 1085 (vs), 1028 (vs), 862 (w), 805 (s).

Calculated for C₁₇H₂₇B₉Zr: C, 48.62; H, 6.48, and found: C, 48.87; H, 6.58.

EXAMPLE 5 Preparation of [η⁵:η⁵-Me₂C(C₅H₄)(C₂B₉H₁₀)]ZrCH₂SiMe₃

A toluene (15 mL) solution of Me₂C(C₅H₅)(C₂B₉H₁₂)(240 mg, 11.0 mmol) was slowly added to a toluene (20 mL) solution of Zr(CH₂TMS)₄ (440 mg, 1.0 mmol) with stirring at −78° C. The reaction mixture was stirred overnight at room temperature. This solution was concentrated under vacuum to about 15 mL from which the title complex was isolated as pale-yellow crystals (253 mg, 61%).

¹H NMR (benzene-d₆): δ 6.65 (m, 1H), 6.23 (m, 1H), 6.20 (m, 1H), 5.91 (m, 1H)(C₅H₄), 2.10 (d, J=9.0 Hz, 1H)(CH₂SiMe₃), 1.97 (s, 1H)(CH of C₂B₉H₁₀), 1.82 (d, J=9.0 Hz, 1H)(CH₂SiMe₃), 1.40 (s, 3H), 0.82 (s, 3H)((CH₃)₂C).

¹¹B NMR (benzene-d₆): δ 3.3 (1), −0.1 (1), −2.5 (1), −5.7 (2), −7.6 (1), −11.1 (1), −12.2 (1), −18.1 (1).

IR (KBr, cm⁻¹): ν 2961 (m), 2921 (m), 2553 (s), 1230 (s), 1152 (w), 1088 (vs), 853 (w), 8795 (s).

Calculated for C₁₄H₃₁B₉SiZr: C, 40.42; H, 7.51, and found: C, 40.61; H, 7.46.

Alternative Method

The title complex was also prepared as pale-yellow crystals from [{[(μ-η⁵):η⁵-Me₂C(C₅H₄)(C₂B₉H₁₀)]Na(THF)}{Na(THF)₃}{Na(THF)₂}]₂ (1.62 g, 1.0 mmmol), ZrCl₄(THF)₂ (0.76 g, 2.0 mmol) and LiCH₂SiMe₃ (11.0M in pentane, 2.0 mmol) in 30 mL of THF using the procedure identical to that described for [η⁵:η⁵-Me₂C(C₅H₄)(C₂B₉H₁₀)]ZrCH₂Ph in Example 4: yield 0.65 g (78%).

EXAMPLE 6 Preparation of [η⁵:η⁵-Me₂C(C₉H₆)(C₂B₉H₁₀)]Zr(NHC₆H₃Me₂-2,6)(THF)

To a THF (25 mL) solution of [Me₂C(C₉H₇)(C₂B₉H₁₁)][Me₃NH] (0.336 g, 0.96 mmol) was added NaH (0.18 g, 7.5 mmol) and the reaction mixture was refluxed for 2 days. After removal of excess NaH by filtration, the resulting solution was added to a suspension of ZrCl₄(THF)₂ (0.362 g, 0.96 mmol) in THF (10 mL) at −78° C. and the mixture was slowly warmed to room temperature and stirred overnight. After removal of the precipitate, to the resulting THF solution was added a THF (5 mL) solution of NaNHC₆H₃Me₂-2,6 (0.137 g, 0.96 mmol) at −78° C., and the reaction mixture was stirred at room temperature for 2 days. The solvent was evaporated under vacuum and the residue was extracted with toluene (15 mL ×3). The toluene solutions were combined and concentrated to about 10 mL. The title complex was isolated as yellow crystals after this solution stood at room temperature for several days (0.32 g, 58%).

¹H NMR (pyridine-d₅): δ 9.38 (s, 1H)(NH), 7.86 (d, J=9 Hz, 1H), 7.37 (d, J=8.4 Hz, 1H), 6.96 (m, 1H), 6.91 (m, 1H), 6.86–6.75 (m, 2H)(C₉H₆), 7.04 (d, J=7.5 Hz, 2H), 6.41 (m, 1H)(NHC₆H₃(CH₃)₂)). 3.64 (m, 4H), 1.59 (m, 4H)(THF), 3.35 (s, 1H)(CH of C₂B₉H₁₀), 2.31 (s, 6H)(NHC₆H₃(CH₃)₂), 1.99 (s, 3H), 1.70 (s, 3H)((CH₃)₂C).

¹³C NMR (pyridine-d₅): δ 154.0, 129.8, 127.7, 126.5, 125.3, 124.7, 123.8, 121.9, 120.8, 118.9, 114.7, 111.8, 110.3, 108.9 (NHC₆H₃(CH₃)₂+C₉H₆), 67.1, 25.1 (THF), 51.1 (C₂B₉H₁₀), 40.7, 29.0, 28.9 ((CH₃)₂C), 20.1, 17.3 (NHC₆H₃(CH₃)₂).

¹¹B NMR (pyridine-d₅): δ4.5 (1), −3.3 (1), −4.6 (1), −6.7 (2), −11.5 (3), −18.6 (1).

IR (KBr, cm⁻¹): ν_(BH)2524 (s).

Calculated for C₂₆H₄₆B₉NOZr: C, 54.10; H, 8.03; N, 2.43, and found: C, 54.33; H, 7.87; N, 2.32.

EXAMPLE 7 Preparation of [η⁵:η⁵-Me₂C(C₉H₆)(C₂B₉H₁₀)]Zr(CH₂C₆H₅)

To a THF (15 mL) solution of [Me₂C(C₉H₇)(C₂B₉H₁₁)][Me₃NH] (0.30 g, 0.86 mmol) was added NaH (0.16 g, 6.66 mmol) and the reaction mixture was refluxed for 2 days. The excess NaH was filtered off and washed with THF (3 mL ×2). The filtrate was added to a suspension of ZrCl₄(THF)₂ (0.325 g, 0.86 mmol) in THF (10 mL) at −78° C. and the mixture was slowly warmed to room temperature and stirred overnight. After removal of the precipitate, the filtrate was added to a THF (10 mL) solution of KCH₂C₆H₅ (0.11 g, 0.86 mmol) at −78° C., and the reaction mixture was slowly warmed to room temperature and stirred overnight. The solvent was evaporated under vacuum and the residue was extracted with DME (5 mL ×3). The DME solutions were combined and concentrated to about 5 mL, form which the title complex was isolated as orange crystals (0.26 g, 65%).

¹H NMR (benzene-d₆): δ 7.74 (d, J=9 Hz, 1H), 7.49 (m, 2H), 7.39 (m, 2H), 7.23–6.80 (m, 4H), 6.71 (d, J=3.6 Hz, 1H), 5.27 (m, J=3.6 Hz, 1H)(CH₂C₆H₅+C₉H₆), 2.60 (s, 2H)(CH₂C₆H₅), 2.20 (s, 1H)(CH of C₂B₉H₁₀), 1.81 (s, 3H), 1.12 (s, 3H)((CH₃)₂C).

¹³CNMR (benzene-d₆): δ 154.8, 130.3, 129.3, 127.0, 126.5, 126.0, 125.6, 124.6, 123.9, 122.1, 121.3, 115.8, 112.4, 104.6 (CH₂C₆H₅+C₉H₆), 70.3 (CH₂C₆H₅), 65.3, 52.0 (C₂B₉H₁₀), 40.7, 29.7, 29.4 ((CH₃)₂C).

¹¹B NMR (benzene-d₆): δ0.9 (1), −0.8 (1), −2.7 (1), −5.5 (1), −7.0 (2), −11.3 (1), −13.3 (1), −20.1 (1).

IR (KBr, cm⁻¹): ν_(BH) 2533 (vs).

Calculated for C₂₁H₂₉B₉Zr: C, 53.67; H, 6.22, and found: C, 53.55; H, 6.16.

EXAMPLE 8 Preparation of [CH₂(C₅H₃Bu₂ ^(t)-2,5)(C₂B₉H₁₁)][Me₃NH]

As shown in FIG. 3, this complex was prepared from CH₂(C₅H₃Bu₂ ^(t)-2,5)(C₂B₁₀H₁₁)(0.385 g, 1.15 mmol) and piperidine (3.0 mL, 30.0 mmol) in ethanol (20 mL) using the same procedure as described for the synthesis of [Me₂C(C₅H₅)(C₂B₉H₁₁)][Me₃NH] in Example 1. The product was further purified by recrystallization from ethanol/hexane to yield the title complex as a white solid (0.41 g, 93%).

¹H NMR (acetone-d₅): δ 6.39 (m, 1H), 6.14 (m, 1H)(C₅H₃), 3.22 (s, 11H) ((CH₃)₃NH+CH₂), 3.01 (s, 1H)(C₅H₃), 1.70 (s, 1H)(CH of C₂B₉H₁₁), 1.25 (s, 6H), 1.20 (s, 3H), 1.00 (s, 3H), 0.94 (s, 6H)((CH₃)₃C), −2.8 (br s, 1H)(B—H—B).

¹³C NMR (acetone-d₅): δ 148.4, 143.4, 142.7, 135.7, 134.3 (C₅H₃), 65.4 (C₂B₉H₁₀), 64.9 (C₅H₃), 46.5 ((CH₃)₃NH), 38.4, 38.3 (CH₂), 34.6, 34.4, 32.1, 31.9 ((CH₃)₃C).

¹¹B NMR (acetone-d₅): δ −15.1 (1), −16.4 (1), −18.8 (1), −21.1 (1), −23.7 (2), −28.3 (1), −38.7 (1), −41.7 (1).

IR (KBr, cm⁻¹): ν_(BH) 2529 (vs).

Calculated for C₁₉H₄₄B₉N: C, 59.45; H, 11.55; N, 3.65, and found: C, 59.32; H, 11.51; N, 3.71.

EXAMPLE 9 Preparation of [CH₂(C₅H₃Bu^(t) ₂-2,4)(C₂B₉H₁₁)][Me₃NH]

This complex was prepared from CH₂(C₅H₃Bu₂ ^(t)-2,4)(C₂B₁₀H₁₁)(0.77 g, 2.30 mmol) and piperidine (6.0 mL, 60.0 mmol) in ethanol (20 mL) using the same procedure described in Example 8. The product was purified by recrystallization from ether/hexane (2:1) to yield the title complex as a white solid (0.79 g, 89%).

¹H NMR (acetone-d₅): δ 6.35 (s), 6.06 (s)(C₅H₃), 3.21 (s, 11H)((CH₃)₃NH+CH₂), 2.93 (m, 2H)(C₅H₃), 1.70 (s, 1H)(CH of C₂B₉H₁₁), 1.15 (m, 18H)((CH₃)₃C), −2.7 (br s, 1H)(B−H−B).

¹³C NMR (acetone-d₅): δ 155.2, 153.6, 145.1, 144.2, 140.2, 130.0, 129.1, 126.2 (C₅H₃), 57.9 (C₂B₉H₁₀), 46.5 ((CH₃)₃NH), 45.4, 41.8 (C₅H₃), 40.7, 40.2 (CH₂), 33.8, 33.7, 32.0, 31.9, 31.6, 31.5 ((CH₃)₃C).

¹¹B NMR (acetone-d₅): δ −9.3 (1), −10.9 (1), −13.3 (1), −16.1 (1), −19.1 (2), −22.0 (1), −33.3 (1), −36.4 (1).

IR (KBr, cm⁻¹): ν_(BH) 2520 (vs).

Calculated for C₁₉H₄₄B₉N: C, 59.45; H, 11.55; N, 3.65, and found: C, 59.56; H, 11.33; N, 3.46.

EXAMPLE 10 Preparation of [η⁵:η⁵-CH₂(C₅H₂Bu₂ ^(t)-2,4)(C₂B₉H₁₀)]Zr(CH₂C₆H₅)

To a THF (20 mL) solution of [CH₂(C₅H₃Bu₂ ^(t)-2,4)(C₂B₉H₁₁)][Me₃NH](0.79 g, 2.06 mmol) was added KH (0.67 g, 16.7 mmol) and the reaction mixture was refluxed for 2 days. The excess KH was filtered off and washed with THF (3 mL ×2). The filtrate was added to a suspension of ZrCl₄(THF)₂ (0.78 g, 2.06 mmol) in THF (20 mL) at −78° C. and the mixture was slowly warmed to room temperature and stirred overnight. After removal of the precipitate, the filtrate was added to a THF (10 mL) solution of KCH₂C₆H₅ (0.27 g, 2.07 mmol) at −78° C., and the reaction mixture was slowly warmed to room temperature and stirred overnight. The solvent was evaporated under vacuum and the residue was extracted with toluene (10 mL ×3). The toluene solutions were combined and concentrated to about 8 mL, from which the title complex was isolated as yellow crystals (0.71 g, 68%).

¹H NMR (benzene-d₆): δ 7.51 (m, 2H), 7.37 (m, 2H), 6.98 (m, 1H)(CH₂C₆H₅), 6.58 (s, 1H), 6.34 (s, 1H)(C₅H₄), 2.84 (s, 2H)(CH₂), 2.58 (s, 2H) (CH₂C₆H₅), 1.47 (s, 9H) (C(CH₃)₃), 1.24 (s, 9H)(C(CH₃)₃).

¹³C NMR (benzene-d₆): δ 155.0, 129.7, 127.1, 126.5, 122.8 (CH₂C₆H₅), 143.1, 137.1, 125.9, 122.5 (C₅H₃), 68.3 (CH₂C₆H₅), 56.6 (C₂B₁₀H₁₁), 37.2 (CH₂), 36.8, 33.8, 33.4 ((CH₃)₃C).

¹¹B NMR (benzene-d₆): δ 4.36 (1), −3.15 (1), −4.45 (1), −8.25 (2), −9.65 (2),

IR (KBr, cm⁻¹): ν_(BH) 2533 (s).

Calculated for C₂₃H₃₇B₉Zr: C, 55.02; H, 7.43; and found: C, 55.35; H, 7.22.

EXAMPLE 11 Preparation of [H₂C(C₅HMe₄)(C₂B₉H₁₁)][Me₃NH]

As shown in FIG. 4, to an ethanol (40 mL) solution of H₂C(C₅HMe₄)(C₂B₁₀H₁₁)(0.85 g, 3.0 mmol) was added piperidine (7.5 mL, 75.0 mmol). The mixture was refluxed for 2 days until the ¹¹B NMR spectrum of the solution showing no peaks corresponding to the starting material. The ethanol and excess piperidine were removed under vacuum, the residue was dissolved in ethanol (5 mL). After filtration, a saturated trimethylammonium hydride chloride solution was added. The sticky solid was filtered off, washed with water and hexane respectively, reprecipitated from acetone to ether, and dried in vacuum for 3 hrs to give the title complex as pale yellow oil (0.78 g, 78%).

¹H NMR (CDCl₃): δ 3.13 (s, 9H)(CH₃ of [Me₃NH]), 3.10 (s, 2H)(CH₂), 1.83 (d, 3H)(CH₃), 1.72 (m, 6H)(CH₃), 1.00 (m, 3H)(CH₃).

¹³C NMR (CDCl₃): δ 142.3, 136.4, 131.9, 131.6 (C₅Me₄), 63.7, 48.2 (C₂B₁₀H₁₁), 47.8 (CH₂), 43.4 ([(CH₃)₃NH]), 33.7 (C₅Me₄), 13.1, 12.5, 9.4, 8.8 (C₅(CH₃)₄).

¹¹B NMR (acetone-d₅): δ −9.9 (1), −10.9 (1), −14.0 (1), −16.9 (1), −18.3 (1), −19.1 (1), −22.3 (1), −33.4 (1), −36.6 (1).

IR (KBr, cm⁻¹): ν_(BH) 2508 (vs).

Calculated for C₁₅H₃₆B₉N: C, 54.97; H, 11.07; N, 4.27, and found: C, 54.68; H, 11.23; N, 4.31.

EXAMPLE 12 Preparation of [η⁵:η⁵-H₂C(C₅Me₄)(C₂B₉H₁₀)]Zr(CH₂TMS)

To a THF (40 mL) solution of [H₂C(C₅HMe₄)(C₂B₉H₁₁)][Me₃NH] (426 mg, 1.3 mmol) was slowly added ^(n)BuLi (4.0 mL, 3.9 mmol) at −78° C. and the mixture was slowly warmed to room temperature. The resultant clear yellow solution was slowly added to a suspension of ZrCl₄(THF)₂ (490 mg, 1.3 mmol) in THF (10 mL) at −78° C. The mixture was slowly warmed to room temperature and stirred overnight. To the resultant solution was slowly added a 1.0 M solution of LiCH₂SiMe₃ in pentane (1.3 mL, 1.3 mmol) at −78° C. The mixture was slowly warmed to room temperature and stirred overnight. After removal of solvent, the residue was extracted with toluene (15 mL ×3). The toluene solutions were combined and concentrated to about 10 mL from which the title complex was isolated as yellow crystals (415 mg, 72%).

¹H NMR (benzene-d₆): δ 2.95 (d, J=14.7 Hz, 1H), 2.63 (d, J=14.7 Hz, 1H) (CH₂), 2.14 (s, 3H)(CH₃), 2.07 (s, 3H)(CH₃), 2.02 (s, 3H)(CH₃), 1.69 (s, 3H)(CH₃), 0.81 (d, J=9.0 Hz, 1H), 0.63 (d, J=9.0 Hz, 1H)(CH₂TMS), 0.38 (s, 9H)(CH₂Si(CH₃)₃).

¹³C NMR (benzene-d₆): δ 124.2, 122.9, 116.8, 113.4, 103.9 (C₅Me₄), 64.5 (CH₂Si(CH₃)₃), 61.9, 49.0 (C₂B₁₀H₁₁), 33.3 (CH₂), 14.1, 12.8, 12.5, 12.4 (C₅(CH₃)₄), 4.2 (CH₂Si(CH₃)₃).

¹¹B NMR (benzene-d₆): δ 0.08 (1), −6.21 (2), −10.12 (1), −13.69 (2), −15.91 (1), −18.90 (1), −22.95 (1).

Calculated for C₁₆H₃₅B₉SiZr: C, 43.28; H, 7.95, and found: C, 43.36; H, 7.85.

EXAMPLE 13 Preparation of [η⁵:η⁵-H₂C(C₅Me₄)(C₂B₉H₁₀)]Hf(CH₂TMS)

This complex was prepared as pale yellow crystals from [H₂C(C₅HMe₄)(C₂B₉H₁₁)][Me₃NH] (426 mg, 1.3 mmol), ^(n)BuLi (4.0 mL, 3.9 mmol), HfCl₄(THF)₂ (605 mg, 1.3 mmol) and LiCH₂SiMe₃ (1.3 mL, 1.3 mmol) in THF using the same procedure described in Example 12: yield 428 mg (62%).

¹H NMR (benzene-d₆): δ 2.92 (d, J=14.7 Hz, 1H), 2.60 (d, J=14.7 Hz, 1H) (CH₂), 2.15 (s, 3H)(CH₃), 2.05 (s, 3H)(CH₃), 2.00 (s, 3H)(CH₃), 1.72 (s, 3H)(CH₃), 0.95 (d, J=9.0 Hz, 1H), 0.68 (d, J=9.0 Hz, 1H)(CH₂TMS), 0.46 (s, 9H)(CH₂Si(CH₃)₃).

¹³C NMR (benzene-d₆): δ 124.1, 122.5, 116.6, 113.5, 103.7 (C₅Me₄), 64.8 (CH₂Si(CH₃)₃), 61.9, 51.0 (C₂B₁₀H₁₁), 33.8 (CH₂), 14.0, 12.5, 12.6, 12.2 (C₅(CH₃)₄), 4.0 (CH₂Si(CH₃)₃).

¹¹B NMR (benzene-d₆): δ 0.18 (1), −6.16 (2), −10.10 (1), −13.50 (2), −15.86 (1), −18.75 (1), −21.98 (1).

Calculated for C₁₆H₃₅B₉HfSi: C, 36.17; H, 6.64, and found: C, 36.33; H, 6.75.

EXAMPLE 14 Ethylene Polymerization (in the Absence of MAO)

This experiment was carried out in a 150 mL glass reactor equipped with a magnetic stirrer and gas inlets. The reactor was charged with the catalyst [η⁵:η⁵-Me₂C(C₅H₄)(C₂B₉H₁₀)]ZrCH₂Ph (3.0 μmol) and toluene (50 mL ). Ethlene gas was then introduced to the reactor at 25° C., and its pressure was maintained continuously at 1 atm by means of bubbling. The polymerization was terminated after 1 h by addition of acidic ethanol (100 mL). The white precipitate was filtered off and washed with ethanol and acetone. The resulting powder was finally dried in a vacuum oven at 80° C. overnight. M_(w) and M_(n) were 4.86×10⁴ and 2.21×10⁴, respectively, and M_(w)/M_(n)=2.20. Catalyst activity was 4.64×10⁶ g polymer/mol Zr-hr-atm ethylene.

EXAMPLE 15 Ethylene Polymerization (in the Presence of MAO)

Ethylene was polymerized as in Example 14 except that methylalumoxane (MAO) was employed as a potential cocatalyst. The reaction mixture contained an Al/Zr ratio of 1,000. Catalyst activity was 4.85×10⁶ g polymer/mol Zr-hr-atm ethylene, showing that activity remains almost the same in the presence of MAO. This suggests that MAO is not an effective cocatalyst.

Other ligands and catalysts shown in Schemes 1–4 were prepared in a similar manner described above.

The specific embodiments described herein are offered by way of examples only. Many modifications and variations of the embodiments described herein may be made without departing from the scope, as is apparent to those skilled in the art. 

1. A bridged cyclopentadienyl-dicarbollide metallocene complex having the formula (I): {L[(Cp)(C₂B₉R¹ ₁₀)]}MR  (I) wherein: Cp is a group selected from the group consisting of cyclopentadienyl, indenyl, tetrahydroindenyl, and fluorenyl, wherein said Cp group is unsubstituted or substituted by one or more radicals selected from the group consisting of C₁–C₁₀ alkyl, C₂–C₁₀ alkenyl, C₃–C₁₀ cycloalkyl, C₁–C₁₀ alkoxy, and C₆–C₁₅ aryl, where each pair of adjacent radicals on the ring together may form a cyclic group; each R¹ is independently hydrogen, halogen, C₁–C₁₀ alkyl, or C₂–C₁₀ alkenyl; L is C₁–C₄ alkylene, which is unsubstituted or substituted by one or more radicals selected form the group consisting of C₁–C₁₀ alkyl, C₂–C₁₀ alkenyl, C₃–C₁₀ cycloalkyl, C₁–C₁₀ alkoxy, C₆–C₁₅ aryl, and Si(R²)₂, wherein each R² is independently selected from the group consisting of hydrogen, C₁–C₁₀ alkyl, C₂–C₁₀ alkenyl, C₁–C₁₀ alkoxy, C₃–C₁₀ cycloalkyl, and C₆–C₁₅ aryl, wherein L bonds to both Cp ring and the cage of C₂B₉R¹ ₁₀; R is selected from the group consisting of hydrogen, halogen, R³, OR³, SR³, NR³R⁴, PR³R⁴, and ZSiR³(R⁴)₂, wherein each R³ is independently selected from the group consisting of C₁–C₁₀ alkyl, C₂–C₁₀ alkenyl, C₃–C₁₀ cycloalkyl, and C₆–C₁₅ aryl, and each R⁴ is independently selected from the group consisting of hydrogen, C₁–C₁₀ alkyl, C₂–C₁₀ alkenyl, C₃–C₁₀ cycloalkyl and C₆–C₁₅ aryl, and Z is C₁–C₁₀ alkylene; and M is Ti, Zr, or Hf.
 2. The complex of claim 1, wherein Cp is cyclopentadienyl or indenyl, wherein said cyclopentadienyl and indenyl is unsubstituted or substituted with one to four substituents selected from the group consisting of C₁ to C₄ alkyl, C₂ to C₄ alkenyl, C₃ to C₆ cycloalkyl, C₁ to C₄ alkoxy, and C₆–C₁₀ aryl, and wherein R¹ is hydrogen.
 3. The complex of claim 2, wherein Cp is C₅H₄, C₅Me₄, C₅H₂(Pr^(i))₂, C₅H₂(Bu^(t))₂ or C₉H₆.
 4. The complex of claim 1, wherein L is C₁–C₄ alkylene, wherein said C₁–C₄ alkylene is unsubstituted or substituted with one or more radicals selected from the group consisting of C₁–C₄ alkyl, C₂–C₄ alkenyl, C₃–C₆ cycloalkyl, C₁–C₄ alkoxy, C₆–C₁₀ aryl, and Si(R²)₂, wherein each R² is independently selected from the group consisting of hydrogen, C₁–C₄ alkyl, C₂–C₄ alkenyl, C₃–C₆ cycloalkyl, C₁–C₄ alkoxy, and C₆–C₁₀ aryl; wherein Cp is C₅H₄, C₅Me₄, C₅H₂(Pr^(i))₂, C₅H₂(Bu^(t))₂ or C₉H₆; and wherein R¹ is hydrogen.
 5. The complex of claim 4, wherein L is CMe₂ or CH₂.
 6. The complex of claim 1, wherein R is selected from the group consisting of R³, OR³, SR³, NR³R⁴, PR³R⁴, and ZSiR³(R⁴)₂, wherein each R³ is independently selected from the group consisting of C₁–C₄ alkyl, C₂–C₄ alkenyl, C₃–C₆ cycloalkyl and C₆–C₈ aryl, and wherein each R⁴ is independently selected from the group consisting of hydrogen, C₁–C₄ alkyl, C₂–C₄ alkenyl, C₃–C₆ cycloalkyl and C₆–C₈ aryl, and Z is C₁–C₄ alkylene; Cp is C₅H₄, C₅Me₄, C₅H₂(Pr^(i))₂, C₅H₂(Bu^(t))₂ or C₉H₆, and R¹ is hydrogen.
 7. The complex of claim 6, wherein R is selected from the group consisting of R³, OR³, NR³R⁴ and ZSiR³(R⁴)₂ wherein each R³ is independently selected from the group consisting of C₁–C₄ alkyl and C₆–C₈ aryl, and wherein each R⁴ is independently selected from the group consisting of hydrogen, C₁–C₄ alkyl and C₆–C₈ aryl, and Z is C₁–C₄ alkylene.
 8. The complex of claim 7, wherein R is CH₂Ph, CH₂Si(CH₃)₃, or NHC₆H₃Me₂-2,6.
 9. The complex of claim 1, wherein M is Zr or Hf; Cp is C₅H₄, C₅Me₄, C₅H₂(Pr^(i))₂, C₅H₂(Bu^(t))₂ or C₉H₆; and R¹ is hydrogen.
 10. The complex of claim 1, wherein L is CMe₂ or CH₂; Cp is C₅H₄ or C₉H₆; R is CH₂Ph, CH₂Si(CH₃)₃, or NHC₆H₃Me₂-2,6; R¹ is H; and M is Zr or Hf.
 11. The complex of claim 1, which is selected from the group consisting of: [η⁵:η⁵-Me₂C(C₅H₄)(C₂B₉H₁₀)]Zr(CH₂C₆H₅), [η⁵:η⁵-Me₂C(C₅H₄)(C₂B₉H₁₀)]Zr(CH₂SiMe₃), [η⁵:η⁵-Me₂C(C₉H₆)(C₂B₉H₁₀)]Zr(NHC₆H₃Me₂-2,6), [η⁵:η⁵-Me₂C(C₉H₆)(C₂B₉H₁₀)]Zr(CH₂C₆H₅), [η⁵:η⁵-CH₂(C₅H₂Bu^(t) ₂-2,4)(C₂B₉H₁₀)]Zr(CH₂C₆H₅), [η⁵:η⁵-H₂C(C₅Me₄)(C₂B₉H₁₀)]Zr(CH₂SiMe₃), and [η⁵:η⁵-H₂C(C₅Me₄)(C₂B₉H₁₀)]Hf(CH₂SiMe₃).
 12. A method for preparing a bridged cyclopentadienyl-dicarbollide metallocene complex of formula (I): {L[(Cp)(C₂B₉R¹ ₁₀)]}MR  (I) wherein: Cp is a group selected from the group consisting of cyclopentadienyl, indenyl, tetrahydroindenyl, and fluorenyl, wherein said Cp group is unsubstituted or substituted by one or more radicals selected from the group consisting of C₁–C₁₀ alkyl, C₂–C₁₀ alkenyl, C₃–C₁₀ cycloalkyl, C₁–C₁₀ alkoxy, and C₆–C₁₅ aryl, where each pair of adjacent radicals on the ring together may form a cyclic group; each R¹ is independently hydrogen, halogen, C₁–C₁₀ alkyl, or C₂–C₁₀ alkenyl; L is C₁–C₄ alkylene, which is unsubstituted or substituted by one or more radicals selected form the group consisting of C₁–C₁₀ alkyl, C₂–C₁₀ alkenyl, C₃–C₁₀ cycloalkyl, C₁–C₁₀ alkoxy, C₆–C₁₅ aryl, and Si(R²)₂, wherein each R² is independently selected from the group consisting of hydrogen, C₁–C₁₀ alkyl, C₂–C₁₀ alkenyl, C₁–C₁₀ alkoxy, C₃–C₁₀ cycloalkyl, and C₆–C₁₅ aryl, wherein L bonds to both Cp ring and the cage of C₂B₉R¹ ₁₀; R is selected from the group consisting of hydrogen, halogen, R³, OR³, SR³, NR³R⁴, PR³R⁴, and ZSiR³(R⁴)₂, wherein each R³ is independently selected from the group consisting of C₁–C₁₀ alkyl, C₂–C₁₀ alkenyl, C₃–C₁₀ cycloalkyl, and C₆–C₁₅ aryl, and each R⁴ is independently selected from the group consisting of hydrogen, C₁–C₁₀ alkyl, C₂–C₁₀ alkenyl, C₃–C₁₀ cycloalkyl and C₆–C₁₅ aryl, and Z is C₁–C₁₀ alkylene; and M is Ti, Zr, or Hf, the method comprising reacting a protonated form of {L[(Cp)(C₂B₉R¹ ₁₀)]}³⁻ with MR₄, wherein L, Cp, R, R¹ or M has the same definition as the above with the proviso that R is different from halogen, or reacting {L[(Cp)(C₂B₉R¹ ₁₀)]}³⁻ with MX₄, followed by substituting X with R if necessary, wherein R is different from halogen and X represents halogen.
 13. The method of claim 12, wherein Cp is cyclopentadienyl or indenyl, wherein said cyclopentadienyl and indenyl is unsubstituted or substituted with one to four substituents selected from the group consisting of C₁ to C₄ alkyl, C₂ to C₄ alkenyl, C₃ to C₆ cycloalkyl, C₁ to C₄ alkoxy, and C₆–C₁₀ aryl, and wherein R¹ is hydrogen.
 14. The method of claim 13, wherein Cp is C₅H₄, C₅Me₄, C₅H₂(Pr^(i))₂, C₅H₂(Bu^(t))₂ or C₉H₆.
 15. The method of claim 12, wherein L is C₁–C₄ alkylene, wherein said C₁–C₄ alkylene is unsubstituted or substituted with one or more radicals selected from the group consisting of C₁–C₄ alkyl, C₂–C₄ alkenyl, C₃–C₆ cycloalkyl, C₁–C₄ alkoxy, C₆–C₁₀ aryl, and Si(R²)₂, wherein each R² is independently selected from the group consisting of hydrogen, C₁–C₄ alkyl, C₂–C₄ alkenyl, C₃–C₆ cycloalkyl, C₁–C₄ alkoxy, and C₆–C₁₀ aryl; wherein Cp is C₅H₄, C₅Me₄, C₅H₂(Pr^(i))₂, C₅H₂(Bu^(t))₂ or C₉H₆; and wherein R¹ is hydrogen.
 16. The method of claim 15, wherein L is CMe₂ or CH₂.
 17. The method of claim 12, wherein R is selected from the group consisting of R³, OR³, SR³, NR³R⁴, PR³R⁴, and ZSiR³(R⁴)₂, wherein each R³ is independently selected from the group consisting of C₁–C₄ alkyl, C₂–C₄ alkenyl, C₃–C₆ cycloalkyl and C₆–C₈ aryl, and wherein each R⁴ is independently selected from the group consisting of hydrogen, C₁–C₄ alkyl, C₂–C₄ alkenyl, C₃–C₆ cycloalkyl and C₆–C₈ aryl, and Z is C₁–C₄ alkylene; Cp is C₅H₄, C₅Me₄, C₅H₂(Pr^(i))₂, C₅H₂(Bu^(t))₂ or C₉H₆, and R¹ is hydrogen.
 18. The method of claim 17, wherein R is selected from the group consisting of R³, OR³, NR³R⁴ and ZSiR³(R⁴)₂ wherein each R³ is independently selected from the group consisting of C₁–C₄ alkyl and C₆–C₈ aryl, and wherein each R⁴ is independently selected from the group consisting of hydrogen, C₁–C₄ alkyl and C₆–C₈ aryl, and Z is C₁–C₄ alkylene.
 19. The method of claim 18, wherein R is CH₂Ph, CH₂Si(CH₃)₃, or NHC₆H₃Me₂-2,6.
 20. The method of claim 12, wherein M is Zr or Hf; Cp is C₅H₄, C₅Me₄, C₅H₂(Pr^(i))₂, C₅H₂(Bu^(t))₂, or C₉H₆; and R¹ is hydrogen.
 21. The method of claim 12, wherein L is CMe₂ or CH₂; Cp is C₅H₄ or C₉H₆; R is CH₂Ph, CH₂Si(CH₃)₃, or NHC₆H₃Me₂-2,6; R¹ is H; and M is Zr or Hf.
 22. A process for olefin polymerization comprising contacting one or more olefin monomers with a complex having the formula (I): {L[(Cp)(C₂B₉R¹ ₁₀)]}MR  (I) wherein: Cp is a group selected from the group consisting of cyclopentadienyl, indenyl, tetrahydroindenyl, and fluorenyl, wherein said Cp group is unsubstituted or substituted by one or more radicals selected from the group consisting of C₁–C₁₀ alkyl, C₂–C₁₀ alkenyl, C₃–C₁₀ cycloalkyl, C₁–C₁₀ alkoxy, and C₆–C₁₅ aryl, where each pair of adjacent radicals on the ring together may form a cyclic group; each R¹ is independently hydrogen, halogen, C₁–C₁₀ alkyl, or C₂–C₁₀ alkenyl; L is C₁–C₄ alkylene, which is unsubstituted or substituted by one or more radicals selected form the group consisting of C₁–C₁₀ alkyl, C₂–C₁₀ alkenyl, C₃–C₁₀ cycloalkyl, C₁–C₁₀ alkoxy, C₆–C₁₅ aryl, and Si(R²)₂, wherein each R² is independently selected from the group consisting of hydrogen, C₁–C₁₀ alkyl, C₂–C₁₀ alkenyl, C₁–C₁₀ alkoxy, C₃–C₁₀ cycloalkyl, and C₆–C₁₅ aryl, wherein L bonds to both Cp ring and the cage of C₂B₉R¹ ₁₀; R is selected from the group consisting of hydrogen, halogen, R³, OR³, SR³, NR³R⁴, PR³R⁴, and ZSiR³(R⁴)₂, wherein each R³ is independently selected from the group consisting of C₁–C₁₀ alkyl, C₂–C₁₀ alkenyl, C₃–C₁₀ cycloalkyl, and C₆–C₁₅ aryl, and each R⁴ is independently selected from the group consisting of hydrogen, C₁–C₁₀ alkyl, C₂–C₁₀ alkenyl, C₃–C₁₀ cycloalkyl and C₆–C₁₅ aryl, and Z is C₁–C₁₀ alkylene; and M is Ti, Zr, or Hf.
 23. The process of claim 22, wherein L is CMe₂ or CH₂; Cp is C₅H₄ or C₉H₆; R is CH₂Ph, CH₂Si(CH₃)₃, or NHC₆H₃Me₂-2,6; R¹ is H; and M is Zr or Hf.
 24. The process of claim 23, wherein the monomer is ethylene or an alpha olefin. 